The present invention relates to a device for the adsorption treatment of a fluid or fluid stream, a use of a device for the adsorption treatment of a fluid or fluid stream, a method for regenerating and/or disposing of, filling and/or installing a device for the adsorption treatment of a fluid or fluid stream and a method for the adsorption treatment of a fluid or fluid stream, in particular natural gas or liquefied gas for fuel cells. The invention relates in particular to a device for desulfurizing a gaseous hydrocarbon stream and a corresponding method, in particular for use in combination with a fuel cell apparatus.
Most fuel cells require hydrogen or hydrogen-rich gases as fuel for producing heat and power. Therefore, significant efforts are currently being made to produce hydrogen from logistic fuels such as diesel, gasoline, naphtha, liquefied gas and natural gas in catalytic fuel-conversion systems. However, in the long term, the successful use of fuel cells depends on the availability of regeneratively-produced hydrogen.
The catalytic conversion of liquid or gaseous hydrocarbons to obtain a hydrogen-rich gas such as the so-called reformate gas takes place in several series-connected steps: the actual reforming reaction, a downstream water-gas shift reaction as well as possibly a CO fine purification reaction such as e.g. the selective CO methanation reaction.
However, most of the primary energy carriers which come into question for the catalytic production of hydrogen contain sulfur. These are sometimes added to the fuel intentionally as so-called odorants to warn people of possible leaks. Odorization serves as a safety measure when using otherwise odourless gases and denotes the addition of odoriferous substances (odorants) which are to have a smell typical of the danger. People associate odorants with alerts, even when the latter are highly diluted. Therefore, in addition to naturally occurring sulfur compounds such as H2 and COS, liquefied gas and natural gas typically contain sulfur-containing odorants such as tetrahydrothiophene (THT) or mercaptans or mixtures of methanethiol, ethanethiol, 1-propanethiol and 2-methyl-2-propanethiol, and tert-butylmercaptan (TBM).
However, it is known that sulfur compounds cause irreversible deactivations in reforming catalysts and in the actual fuel cells. A suitable desulfurization stage is therefore a prerequisite for using hydrocarbons as fuel in a fuel cell. The process-engineering conversions involved in the desulfurization differ greatly depending on the hydrocarbon used. To desulfurize natural gas and liquefied gas, the simplest possible adsorptive desulfurization stages are sought, which can be operated with the highest possible selectivity at room temperature and ambient pressure.
Adsorptive desulfurization methods with solid adsorbents are used in many fuel cell applications and are relatively simple to realize in terms of process requirements, e.g. room temperature and ambient pressure. For example WO 2010/023249 A1 describes an adsorber material and a method for desulfurizing hydrocarbon-containing gases. However, on the other hand, low temperatures and reaction pressures mean comparatively low sulfur-absorption capacities. The consequence is relatively large adsorber beds or rapid replacement intervals. The capacity of the respective adsorbent depends greatly on the composition of the hydrocarbon as well as on the concentration and type of the sulfur compounds. The materials used are e.g. standard and impregnated activated charcoals, zeolite systems, metal and mixed-metal (oxide) catalysts, clay minerals as well as combinations of the materials in mixed bed and multi-component systems.
There is a demand for devices for adsorption treatment, e.g. detoxifying, of fluids or fluid streams, or for desulfurizing hydrocarbons for fuel cells, which make possible the safety-relevant measures and functionalities when installing or removing the devices in or from the gas line. The safe installation or safe replacement of the device is a central question for a logistical plan for equipping and retrofitting e.g. fuel-cell systems with sulfur filter systems.
The transport of spent desulfurizing cartridges represents one of the most important challenges to be met when constructing a logistical concept for supplying and disposing of desulfurizing cartridges for fuel cells. Filters are generally replaced by service engineers or gas engineers, most of whom have received no special training in dealing with hazardous materials. For this reason, among others, desulfurizing adsorbents are developed which are not classified as hazardous materials. After use, however, depending on the material and according to the accompanying gas substances of the gas to be desulfurized, various other toxic gas constituents in addition to sulfur compounds can accumulate in the adsorbents and thus change their properties.
For this reason, there can be no generally valid classification of the adsorbent in a spent desulfurizing cartridge. Depending on the adsorbent and gas composition, in addition to the sulfur compounds, various other substances may or may not be adsorbed. To protect people from possible exposure it must be ensured that the spent adsorbent is replaced by arranging for only people with expertise and safety equipment to replace the cartridge. Therefore there is a demand for safe devices for adsorption treatment, e.g. devices for the desulfurization of gaseous hydrocarbons.